The present invention relates to a rotating machine, such as a generator or an electric motor for wind power plant, and traction cable plant. The rotating machine generally comprises a bearing, an annular stator supporting the bearing, an annular, turnable rotor facing the stator and supported by the bearing, and, connected to the rotor, a drive arrangement. In embodiments employed as electrical generators or motors, one of the stator or rotor will carry permanent magnets or other magnetic field generators, while the other of the stator and the rotor will carry windings, the magnetic field generators and the windings being disposed on opposing surfaces of the stator and of the rotor.
Preferred embodiments are particularly suited for wind powered machines, such as large scale electrical generators, and the drive arrangement in such embodiments includes blades mounted on a hub attached to the rotor so that the rotor rotates when wind passes over the blades. Large scale wind powered electrical generators are becoming more common, particularly in onshore and offshore wind farm applications. In such large scale generators, a tower supports a nacelle housing the stator, which supports the rotor, which supports the drive arrangement, such as a hub and blades. Equipment required for controlling the generator, including controls for the blades and other machinery, can be housed in the tower, the nacelle, and/or in cavities within the stator and/or the rotor. Embodiments preferably are particularly suited for use in an annular variety of such rotating machines in which an annular stator faces an annular rotor. Preferably, the rotor rotates within the stator and carries the magnetic field generators, such as permanent magnets, on an external surface of the rotor. The windings or coils are carried on an inner surface of the stator facing the rotor. It should be clear that the rotor could rotate outside the stator and/or the magnetic field generators could be carried on the stator. The machines are sized and arranged to enable human passage into the interior of the rotor.
In rotating machines of this type, particularly the annular variety, a problem arises in that the magnetic field generators, such as permanent magnets, as well as the windings, are difficult to maintain and repair. In the preferred annular arrangement in which the rotor rotates within the stator, access to the stator elements is blocked from inside the machine by the rotor. In most cases the rotating machine components must be entirely removed or disassembled in order to obtain access to the point of a fault or to get access to a part to be maintained. It is sometimes necessary to remove virtually the complete stator or rotor in order to bring a component to the workshop and to repair or maintain it. This can be quite cumbersome since the parts involved can be quite heavy and difficult to manage and/or transport when they are atop a fifteen meter high or taller support tower.
A generator is described in the international patent application WO 2004/017497 A1 where simple mounting and dismounting of individual generator components is possible. In this case, however, only one particular arrangement of annular windings and the same armature is provided, which are disposed so as to be sequential. That is, the generator is constructed with an axial arrangement of axially-alternating rotors and stators. The rotors and stators are of similar radial dimension and are broken into segments. However, because of the axial arrangement of the components, the issue of access to the annular stator surrounding an annular rotor, or vice versa, is not addressed.
Another generator is disclosed in U.S. Pat. No. 5,844,341 to Spooner et al. Spooner et al. employ a modular rotor comprising concentric, axially spaced rotor rings mounted on a shaft with spokes. Pairs of the axially-spaced rotor rings support magnet modules that can be installed and removed in a radial direction, the modules being attached to the rings with bolts extending axially through the rings into radially and circumferentially extending mounting plates. While Spooner et al. employ a modular rotor, they do so in a spoked wheel type generator that does not encounter the issues an annular generator has regarding mounting of the rotor segments and access to the stator components. The Spooner et al. solution can not be employed in an annular generator since the rotor segments are supported only at their ends, which would be insufficient in an annular generator.
Embodiments disclosed herein provide a circumferentially segmented rotating machine, such as an annular wind powered generator, in order to be able to mount, repair, and maintain the rotating device in a simpler manner by providing easy access to components of the rotating machine. Embodiments achieve easy access to the components of the rotor and stator by providing a circumferentially segmented rotor and a circumferentially segmented stator. The stator segments are attached to the stator/housing with bolts extending radially to the exterior of the stator and are disposed so that the stator segments are adjacent to one another. The rotor segments are preferably mounted in an annular rotor ring via openings in the rotor ring. A base preferably allows easy axial removal of each rotor segment by engaging axially-extending edges of a respective axial mounting slot formed in the rotor ring to extend from one edge of the rotor ring axially into the ring. Like the stator segments, the rotor segments are disposed so as to be adjacent to one another. When a rotor segment is removed by sliding it out of the rotor ring in an axial direction, one or more stator segments can be accessed through the exposed opening of the empty mounting slot. If the mounting slots, rotor segments, and stator segments are sized properly, then the stator segments can be removed through the openings of the mounting slots, such as in a substantially radial direction.
In a preferred embodiment, each rotor segment comprises at least one permanent magnet and each stator segment has at least one winding. Each rotor segment preferably is disposed on a base which is provided with a profile shaped to prevent radial and circumferential motion of the segment while allowing axial movement of the segment. For example, a dovetail-shaped profile which engages the edges of the mounting slot in the rotor ring with grooves in sides of the profile can be employed. Thus, each rotor segment can be removed in the axial direction without the entire rotor having to be removed. It should again be noted that, while embodiments are described with the rotor carrying magnets and the stator carrying windings or coils, the stator could instead carry magnets while the rotor could instead carry windings or coils.